Wave modes in a magnetoplasma with anisotropic perturbation pressure–fluid and kinetic calculations

2004 ◽  
Vol 70 (4) ◽  
pp. 463-479 ◽  
Author(s):  
C. ALTMAN ◽  
K. SUCHY
Keyword(s):  
Acoustic Mode ◽  
Anisotropic Pressure ◽  
Particle Interactions ◽  
Additional Information ◽  
Fluid Analysis ◽  
Quintic Equation ◽  
Kinetic Calculations ◽  
Perturbation Pressure ◽  
Good Agreement ◽  
Wave Modes

The fluid quintic dispersion equation and the full kinetic Boltzmann–Vlasov equation have been programmed for a one-species magnetoplasma in a form permitting direct comparison between them. The quintic equation yields five wave-modes, two electromagnetic, a Langmuir or Bernstein mode and two transversely polarized acoustic modes driven by the trace-free part of the anisotropic pressure tensor. The slower acoustic mode is found in the kinetic analysis to be evanescent, the other suffers appreciable Landau damping except in the first gyroharmonic band when its phase velocity approaches and even exceeds that of the Langmuir mode, with a resultant mixing of modal properties. The Langmuir or Bernstein mode refractive index surfaces found in the fluid and kinetic analyses are generally in good agreement, but gyroharmonic wave–particle interactions seen in the Bernstein modes are missed in the fluid analysis, such as resonant effects very close to the gyroharmonic frequencies and strong damping at all propagation angles when the wave frequency lies in a forbidden Bernstein region. In all cases the fluid analysis provides additional information on wave polarization and generalized energy fluxes–electromagnetic and acoustic–permitting easy identification of modes.

Alfvén modes in a two-species magnetoplasma with anisotropic perturbation pressure-fluid and kinetic calculations

2007 ◽  
Vol 73 (4) ◽  
pp. 455-471
Author(s):  
C. ALTMAN ◽  
K. SUCHY
Keyword(s):  
Energy Flux ◽  
Acoustic Mode ◽  
Acoustic Energy ◽  
Moderate Increase ◽  
Pressure Tensor ◽  
Ion Temperature ◽  
Fluid Analysis ◽  
Dominant Component ◽  
Kinetic Calculations ◽  
Perturbation Pressure

AbstractThe octic fluid dispersion equation, the kinetic Boltzmann–Vlasov equation and the MHD (scalar pressure) analysis, programmed for a two-species collisionless magnetoplasma in a form permitting direct comparison between them, have been applied to the study of the Alfvén modes in both low- and high-β plasmas. In the low-βregime all methods give essentially the same solutions for the isotropic fast magnetosonic and the field-guided shear Alfvén modes. The real part of the refractive index of the field-guided slow magnetosonic acoustic mode is almost identical in the fluid and kinetic analyses, but is 50% too high in the MHD analysis owing to neglect of the trace-free part of the pressure tensor which drives almost half of the acoustic energy flux. The strong damping of the acoustic mode in both low- and high-β plasmas is drastically reduced by increase of electron temperature, whereas a moderate increase in the perpendicular ion temperature is sufficient to eliminate shear Alfvén damping in high-β plasmas and even to produce wave growth, the effect being more pronounced the higher the plasma β. The fluid analysis shows the electromagnetic energy flux to be negligible in the acoustic mode, in which the acoustic flux is driven both by the trace-carrying and trace-free parts of the pressure tensor, but is usually the dominant component in the (fast) magnetosonic mode.

Estimation of the Thermodynamic Properties of Branched Hydrocarbons

2000 ◽  
Vol 122 (3) ◽  
pp. 147-152 ◽  
Author(s):  
Hui He ◽  
Mohamad Metghalchi ◽  
James C. Keck
Keyword(s):  
Thermodynamic Properties ◽  
Degrees Of Freedom ◽  
Statistical Thermodynamic ◽  
Motion Modes ◽  
Branched Alkanes ◽  
Branched Hydrocarbons ◽  
Wide Range ◽  
On Line ◽  
Kinetic Calculations ◽  
Good Agreement

A simple model has been developed to estimate the sensible thermodynamic properties such as Gibbs free energy, enthalpy, heat capacity, and entropy of hydrocarbons over a wide range of temperatures with special attention to the branched molecules. The model is based on statistical thermodynamic expressions incorporating translational, rotational and vibrational motions of the atoms. A method to determine the number of degrees of freedom for different motion modes (bending and torsion) has been established. Branched rotational groups, such as CH3 and OH, have been considered. A modification of the characteristic temperatures for different motion mode has been made which improves the agreement with the exact values for simple cases. The properties of branched alkanes up to 2,3,4,-trimthylpentane have been calculated and the results are in good agreement with the experimental data. A relatively small number of parameters are needed in this model to estimate the sensible thermodynamic properties of a wide range of species. The model may also be used to estimate the properties of molecules and their isomers, which have not been measured, and is simple enough to be easily programmed as a subroutine for on-line kinetic calculations. [S0195-0738(00)00902-X]

LEARNINGS FROM SPECTRAL GR MEASUREMENTS FROM LWD AND FROM CUTTINGS IN HIGH AND LOW ANGLE WELLS

2021 ◽  
Author(s):  
Mohamed Azizi Ibrahim ◽  
◽  
Faisal Al-Enezi ◽  
Marie Van Steene ◽  
Alan Fernandes ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Potassium Feldspar ◽  
Heavy Minerals ◽  
High Angle ◽  
Volume Calculation ◽  
X Ray ◽  
Additional Information ◽  
Elemental Concentrations ◽  
Depth Control ◽  
Good Agreement

Spectral gamma-ray (SGR) data were acquired from a new slim logging-while-drilling (LWD) tool and from surface cuttings in a near vertical well and in a horizontal well across clastic deposits. Comparison of the data from both measurements indicates that there are advantages from both methods. X-ray diffraction (XRD) and X-ray fluorescence (XRF) data from cuttings also support the findings. The formation evaluation objective is to quantify the volumes of each mineral and fluid present in the formation. SGR data brings the required additional information to reduce the mineral volume uncertainty, especially for the clays in the formation with complex mineral assemblages. In the studied clastic deposits, several clay types are present (with the dominant contribution from illite and kaolinite) together with feldspars and trace elements like zircon and other heavy minerals. The presence of gas introduces another unknown, since it affects the porosity measurements and fluid volume calculation through bulk density and neutron porosity. The comparison of SGR data from LWD logs and from cuttings brings robustness to our conclusions. Comparison of the thorium, potassium, and uranium concentrations from LWD logs and from cuttings shows good agreement in the measurements for the low-angle well. The high-angle well data also shows good agreement between the two measurements except for the cleaner sand section. The results from the cuttings are affected by the accuracy of sample depth control due to the poor borehole conditions and inefficiency in evacuating cuttings in high-angle wells compared to low-angle wells. The trend of the SGR is maintained. The LWD SGR elemental concentrations are then used to solve the formation mineral fractions, which are compared with the same fractions from the XRD on cuttings. Similar conclusions are drawn for the elemental concentrations. The potassium concentration enables the quantification of illite and potassium feldspar. Uranium brings a significant contribution to the total GR measurement, which could lead to a clay volume overestimation if the uranium contributions weren’t excluded. In conclusion, LWD provides superior quality SGR data compared with SGR from cuttings because of the better depth control and vertical resolution. SGR on cuttings can be an alternative when combined with other LWD measurements and accepting a higher uncertainty, in case LWD SGR cannot be run due to certain borehole conditions. This paper compares the results of a slim tool LWD and cuttings SGR data for the first time and concludes on the applicability of each technique.

scholarly journals Plasma Waves in the Inner Magnetosphere

2021 ◽  
pp. 85-119
Author(s):  
Hannu E. J. Koskinen ◽  
Emilia K. J. Kilpua
Keyword(s):  
Radiation Belt ◽  
Low Frequency ◽  
Plasma Waves ◽  
Mhd Waves ◽  
Particle Interactions ◽  
Inner Magnetosphere ◽  
Very Low Frequency ◽  
Link Type ◽  
Wave Modes

AbstractUnderstanding the role of plasma waves, extending from magnetohydrodynamic (MHD) waves at ultra-low-frequency (ULF) oscillations in the millihertz range to very-low-frequency (VLF) whistler-mode emissions at frequencies of a few kHz, is necessary in studies of sources and losses of radiation belt particles. In order to make this theoretically heavy part of the book accessible to a reader, who is not familiar with wave–particle interactions, we have divided the treatise into three chapters. In the present chapter we introduce the most important wave modes that are critical to the dynamics of radiation belts. The drivers of these waves are discussed in Chap. 10.1007/978-3-030-82167-8_5 and the roles of the wave modes as sources and losses of radiation belt particles are dealt with in Chap. 10.1007/978-3-030-82167-8_6.

Estimation of the Thermodynamic Properties for Branched Hydrocarbons

1999 ◽  
Author(s):  
Hui He ◽  
Mohamad Metghalchi ◽  
James C. Keck
Keyword(s):  
Thermodynamic Properties ◽  
Degrees Of Freedom ◽  
Statistical Thermodynamic ◽  
Motion Modes ◽  
Branched Alkanes ◽  
Branched Hydrocarbons ◽  
Wide Range ◽  
On Line ◽  
Kinetic Calculations ◽  
Good Agreement

Abstract A simple model has been developed to estimate the sensible thermodynamic properties such as Gibbs free energy, enthalpy, heat capacity, and entropy of hydrocarbons over a wide range of temperatures with special attention to the branched molecules. The model is based on statistical thermodynamic expressions incorporating translational, rotational and vibrational motions of the atoms. A method to determine the number of degrees of freedom for different motion modes (bending and torsion) has been established. Branched rotational groups, such as CH3 and OH, have been considered. A modification of the characteristic temperatures for different motion mode has been made which improves the agreement with the exact values for simple cases. The properties of branched alkanes up to 2,3,4-Trimthylpentane have been calculated and the results are in good agreement with the experimental data. A relatively small number of parameters are needed in this model to estimate the sensible thermodynamic properties of a wide range of species. The model may also be used to estimate the properties of molecules and their isomers, which have not been measured, and is simple enough to be easily programmed as a subroutine for on-line kinetic calculations.

Two-fluid Analysis of the Geodesic Acoustic Mode in Tokamaks

2011 ◽  
Author(s):  
Akira Hirose ◽  
Jan Weiland ◽  
Jan Weiland ◽  
Enzo Lazzaro
Keyword(s):  
Acoustic Mode ◽  
Fluid Analysis ◽  
Geodesic Acoustic Mode ◽  
Two Fluid

Numerical Study of the Influence of Horizontal Tube Banks on the Hydrodynamics of a Dense Gas-Solid Bubbling Fluidized Bed

2003 ◽  
Vol 1 (1) ◽  
Author(s):  
Sanjib K. Das Sharma ◽  
Ratan Mohan
Keyword(s):  
Fluidized Bed ◽  
Solid Phase ◽  
Numerical Study ◽  
Horizontal Tube ◽  
Particle Interactions ◽  
Tube Bank ◽  
Bubbling Fluidized Bed ◽  
Tube Banks ◽  
Fluidizing Medium ◽  
Good Agreement

Numerical study of the influence of tube-bank on the hydrodynamics of a freely bubbling fluidized bed is relatively less reported in the literature. In this paper, results obtained from CFD study of a two dimensional gas-solid fluidized beds with horizontal tube-bank are compared with the published experimental data (Hull et. al., 1999). A 2-D bed, 1 m high and 0.2 m wide with tubes of diameter 0.026 m was taken for the calculations. Two different tube arrangements of staggered and inline pitch with center-to-center distance of 0.05 m were considered. Air was used as the fluidizing medium and ballotini glass (diameter: 230 mm and density: 2723 kg/m3) was the fluidized material. Air velocities used were 0.15 m/s and 0.187 m/s. The Eulerian-Eularian Two-Fluid CFD model was employed for modeling the momentum equations for both the gas and the solid phase with kinetic theory modification for the solid phase to account for the inter-particle interactions. Hydrodynamic features, such as, bubble size and bubble rise velocity and their variation with height within and outside the tube bank showed good agreement with the data of Hull et al.(1999)

Causal linear parametric model for baroreflex gain assessment in patients with recent myocardial infarction

2001 ◽  
Vol 280 (4) ◽  
pp. H1830-H1839 ◽  
Author(s):  
Giandomenico Nollo ◽  
Alberto Porta ◽  
Luca Faes ◽  
Maurizio Del Greco ◽  
Marcello Disertori ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Frequency Domain ◽  
Autoregressive Model ◽  
Systolic Arterial Pressure ◽  
Frequency Domain Analysis ◽  
Noninvasive Methods ◽  
Additional Information ◽  
Clinical Measurements ◽  
The Time Domain ◽  
Good Agreement

Spectral and cross-spectral analysis of R-R interval and systolic arterial pressure (SAP) spontaneous fluctuations have been proposed for noninvasive evaluation of baroreflex sensitivity (BRS). However, results are not in good agreement with clinical measurements. In this study, a bivariate parametric autoregressive model with exogenous input (ARXAR model), able to divide the R-R variability into SAP-related and -unrelated parts, was used to quantify the gain (αARXAR) of the baroreflex regulatory mechanism. For performance assessing, two traditional noninvasive methods based on frequency domain analysis [spectral, baroreflex gain by autogressive model (αAR); cross-spectral, baroreflex gain by bivariate autoregressive model (α2AR)] and one based on the time domain [baroreflex gain by sequence analysis (αSEQ)] were considered and compared with the baroreflex gain by phenylephrine test (αPHE). The BRS evaluation was performed on 30 patients (61 ± 10 yr) with recent (10 ± 3 days) myocardial infarction. The ARXAR model allowed dividing the R-R variability (950 ± 1,099 ms2) into SAP-related (256 ± 418 ms2) and SAP-unrelated (694 ± 728 ms2) parts. αAR (12.2 ± 6.1 ms/mmHg) and α2AR (8.9 ± 5.6 ms/mmHg) as well as αSEQ (12.6 ± 7.1 ms/mmHg) overestimated BRS assessed by αPHE (6.4 ± 4.7 ms/mmHg), whereas the ARXAR index gave a comparable value (αARXAR = 5.4 ± 3.3 ms/mmHg). All noninvasive methods were significantly correlated to αPHE (αARXAR and αSEQ were more correlated than the other indexes). Thus the baroreflex gain obtained describing the causal dependence of R-R interval on SAP showed a good agreement with αPHE and may provide additional information regarding the gain estimation in the frequency domain.

Die Umwandlung des Cristobalits

1959 ◽  
Vol 14 (10) ◽  
pp. 912-919
Author(s):  
O. Krisement ◽  
G. Trömel
Keyword(s):  
Gaussian Distribution ◽  
Free Energies ◽  
Transformation Temperatures ◽  
Additional Information ◽  
Distribution Of Values ◽  
Good Agreement

The α ⇋ β inversion of cristobalite has been investigated by observing optically the transformation of a sufficiently great number of single cristais of microscopic size. The derived transformationtemperature-function (Mengenkurve) is in good agreement with data from microcalorimetric measurements. Additional information is obtained from the distribution of the transformation temperatures of individual cristais. The behavior of the α ⇋ β inversion is determined by the superposition of two effects: the GAussian distribution of the temperatures, for which the free energies of a- and β-phases are equal, and the GAussian distribution of values for the hysteresis.

Effects of boundary walls on the properties of settling spheres

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sadia Haider ◽  
Atta Ullah ◽  
Adnan Hamid
Keyword(s):  
Volume Fraction ◽  
Fluid Model ◽  
Solid Volume Fraction ◽  
Stokes Number ◽  
Particle Interactions ◽  
Kinetic Trap ◽  
Side Walls ◽  
Two Fluid Model ◽  
The Many ◽  
Good Agreement

Abstract Numerical Simulations are performed, using Eulerian two fluid model (TFM) to investigate the effects of solid volume fraction and no-slip side walls on the settling particles. It is found that average settling velocity decreases with increasing volume fraction for both gas-solid (GS) and liquid-solid (LS) systems, in good agreement with the Richardson-Zaki 1 − ϕ n ${\left(1-\phi \right)}^{n}$ law. It was also noted that average velocity is independent of the boundary condition for both gas-solid (GS) and liquid-solid (LS) systems. The root mean square value of the solid volume fraction shows the increasing trend with volume fraction, caused by the many particle interactions. Furthermore, no-slip sidewalls were found to damp the velocity fluctuations quantitively, while following the well-known ϕ 1 / 2 ${\phi }^{1/2}$ scaling with volume fraction. Side walls were found to act as kinetic trap for the particles, damping the fluctuation near the walls and plateauing in the mid plane. These simulations showed that the GS system shows the higher solid fraction fluctuations that the LS system at the same Reynolds number, mainly because of the higher collision frequency (higher Stokes number) among the particles.

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